ENDURANCE TRAINING INCREASES EXPRESSION OF HEAT SHOCK PROTEIN IN SKELETAL MUSCLE

Abstract

1161 Heat shock proteins (HSPs) play an essential role in maintaining cellular homeostasis during episodes of acute stress. Recent evidence suggests that a single bout of exhaustive exercise increases the expression of the inducible form of the 70kDa family of HSPs (HSP72) in skeletal muscles. Limited data exists regarding the expression of HSP72 in tissues after exercise training. Therefore, these experiments examined the effects of 12 weeks of endurance exercise training on the expression of HSP72 in skeletal muscles. Female Sprague-Dawley rats (120 days old) were assigned to either a sedentary control group or to an endurance exercise training group. Trained animals exercised on a treadmill @ ≈ 70% VO2 max for 12 weeks (4-5 days/wk) at 90 min/day. Upon completion of the training program, the soleus (SOL), plantaris(PLA), extensor digitorum longus (EDL), and the red (RG) and white portions(WG) of the gastrocnemius muscles were excised, and frozen for subsequent biochemical analysis. Skeletal muscle proteins were separated by SDS-PAGE and immunoblotted for HSP72. Exercise training elevated the oxidative capacity of all muscles investigated as demonstrated by increases (p<0.05) in citrate synthase activity. Further, exercise training promoted large and significant increases in HSP72 in all muscles studied (p<0.05). These results indicate that endurance exercise training increases the expression of HSP72 in active skeletal muscles. We postulate that this exercise-induced increase in HSP72 may provide cellular protection against oxidative stress.